Hitherto, there has been known a technology in which the current location of a vehicle on which a navigation device is mounted is acquired on the basis of a GPS signal transmitted from a GPS satellite. For example, Japanese Patent Application Publication No. 10-141968 (JP 10-141968 A) discloses a navigation device configured to specify the current location on the basis of a GPS signal, and further discloses a technology in which it is determined that the vehicle is traveling on an in-tunnel road at a high probability in the case where the position cannot be measured in accordance with a GPS signal.
Hitherto, in addition, there has been developed a technology for specifying the current location without using a GPS signal. For example, a technology in which frequency-region information including the radio wave frequency and the service area of analog broadcast as information is kept and the reception frequency obtained by scanning the analog broadcast radio wave band and the radio wave frequency in the frequency-region information are contrasted with each other to find the current region is known from Japanese Patent Application Publication No. 2006-333180 (JP 2006-333180 A).